606 The American Naturalist. [July, 
skeleton is unknown. The nearest approach to Rhabdosteus is 
made by the genus Stenodelphis. In Cetophis, the caudal centra 
have one face very convex, offering greater flexibility than is pos- 
sible in any other genus. The C. keteroclitus is from the Mary- 
land Miocene. A genus Lophocetus has been established for the 
Delphinus calvertensis of Harlan, also from the Maryland Miocene. 
Its position is uncertain ; the skull resembles that of Inia, but the 
roots of the teeth are cylindric. 
The temporal and occipital 
ridges are very strong. Skele- 
ton unknown.  Delphinodon 
Leidy is represented by teeth 
only, from N. American local- 
ities, but a skull is described 
by Burmeister from Buenos 
Ayres, which shows that the 
nostrils are much more anter- 
ior in position than in Lopho- - 
cetus. 
Extinct and recent forms 
about equally divide the PHY- 
SETERIDE, but the largest 
dimensions are reached by the 
recent sperm whale, Physeter 
macrocephalus L. The modi- 
T fications of the family type 
Fic. 3—Priscodelphinus grandaevus are chiefly those of the denti- 
eid cartes eure N. lira) = tion, but the skull develops 
5, do. proximal extremity; c, mambrium Crests of a peculiar character 
e emcees espa galas € in a number of the genera. 
These are distinguished as Stowe: 
I. Lower jaw with numerous teeth. 
4, Teeth with crown and root continuous, and without 
enamel nion and temporal ridges forming a crest 
| which encloses a basin-shaped cavity of the front. 
i Zygoma complete; symphysis mandibuli long; Physeter® Linn. 
E Eucetus DuBus. ; Physetodon McCoy ; Stenodon VanBen= Orycterocetus Leidy. 
